- Initiation of exercise: At the start of an exercise, neural changes including stimulation of the limbic system, sending of sensory impulses from proprioceptors in the muscles, tendons, and joints, and the sending of motor impulses from the precentral gyrus occurs where impulses will then be sent to be medullary respiratory center in the medulla oblongata. As a result, the medulla oblongata will stimulate an increase in the respiratory rate and depth of an individual.
- Moderate exercise: During moderate exercise, there will be more increase in the respiratory depth and a gradual increase in breathing than at the onset of an exercise. Since muscles contract more which consumes higher amounts of oxygen and produces higher amounts of carbon dioxide, the heart and lungs work harder to keep up with the demands of oxygen by the body.
- Abrupt ascent into high altitudes: Air pressure and oxygen levels at high altitudes are decreased, therefore less amounts of oxygen are available for breathing, and this is sensed by the body’s peripheral chemoreceptors which stimulate an increase in the breathing rate of an individual. This change is the body’s way of making sure that there will be adequate oxygen transported throughout the body.
- Paralysis of phrenic nerve: The phrenic nerve plays a vital role in respiration by helping the diaphragm contract for inhalation and expand/relax for exhalation. When paralyzed, it causes respiratory difficulties, shortness of breath, and a decrease in respiratory depth with more severe cases calling the need for mechanical ventilation.
- Severe anemia: Anemia is a blood disease where the levels of red blood cells containing hemoglobin, a protein responsible for oxygen delivery to the body, are too low, thereby causing a limited supply of oxygen to be used. As a result, the lungs increase their ventilatory drive, increasing the respiratory rate.
- Advanced pregnancy: As the course of pregnancy lengthens, there will be higher levels of progesterone, hormones responsible for increasing the respiratory center’s sensitivity to carbon dioxide and dilating smooth muscles in the airways, resulting in higher respiratory depth and rate. Moreover, the distension of the uterus causes elevation of the diaphragm and more pressure against it which causes the mother to have breathing difficulties and an increased respiratory rate.
References:
Ben-Joseph, E. P. (2023, January). Why Do Some Women Feel Short of Breath During Pregnancy? Nemours KidsHealth. https://kidshealth.org/en/parents/breathing.html
Guo, J., Zhou, C., Xiao, Q., Gong, S. S., Zhao, Q., Wang, L., He, J., Yang, W., Shi, X., Sun, X., & Liu, J. (2015). Impact of anaemia on lung function and exercise capacity in patients with stable severe chronic obstructive pulmonary disease. BMJ Open, 5(10), e008295. https://doi.org/10.1136/bmjopen-2015-008295
Libretexts. (2023, January 17). 21.11B: Adjustments at High Altitude. Medicine LibreTexts. https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Anatomy_and_Physiology_(Boundless)/21%3A_Respiratory_System/21.11%3A_Respiratory_Adjustments/21.11B%3A_Adjustments_at_High_Altitude
LoMauro, A., & Aliverti, A. (2015). Respiratory physiology of pregnancy. Breathe, 11(4), 297–301. https://doi.org/10.1183/20734735.008615
Phrenic nerve. (2022). Cleveland Clinic. https://my.clevelandclinic.org/health/body/22270-phrenic-nerve
Tortora, & Derrickson. (2017). Chapter 23: The Respiratory System. Principles of Anatomy and Physiology (15th ed., pp.888-889). Wiley.